1. Field
The present specification generally relates to methods for extracting glass substrates from glass sheets and, more specifically, to methods for extracting strengthened glass substrates from glass sheets.
2. Technical Background
Thin glass substrates have a variety of applications in consumer electronic devices. For example, such glass substrates may be used as cover sheets and/or touch screens for LCD and LED displays incorporated in mobile telephones, GPS devices, display devices such as televisions and computer monitors and various other electronic devices. As use the use of glass substrates in various devices continues to expand, the geometric complexity of the glass substrates also increases. For example, certain applications may require that the glass substrates be formed with complex shapes, such as curved peripheries and/or through-features, thus requiring additional machining operations to achieve the desired geometry.
The glass substrates may be formed by separating a glass sheet into a plurality of discrete glass. The glass sheet may formed from damage resistant glass, such as ion-exchanged glass or similarly strengthened glass. For example, the ion-exchange process creates a compressive stress at the surfaces of the glass substrate. These compressive stresses extend beneath the surface of the glass substrate to a certain depth, referred to as the depth of layer. The compressive stresses are balanced by a layer of tensile stresses (referred to as central tension) such that the net stress in the glass substrate is zero. The formation of compressive stresses at the surface of the glass substrate counters crack propagation in the compressive layer and, as such, mitigates catastrophic failure of the glass substrate for flaws which do not extend through the depth of layer.
However, strengthened glass substrates are susceptible to edge damage, especially after the glass substrates are separated from a glass sheet after the strengthening process has been performed. More specifically, separating the glass substrate after ion-exchange processing leaves the central tension layer exposed at the edges of the glass substrate, thereby leaving the edge susceptible to damage which may lead to catastrophic failure.
Moreover, when a glass substrate is intended for use as a touch screen, electrically conductive coatings may be applied to the glass substrate. Such coatings are commonly applied to a glass sheet prior to separating the glass sheet into a plurality of discrete glass substrates. However, these coatings are not able to withstand the ion-exchange process, thus compounding the aforementioned problems.